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923b2919e2
In an x86 PV guest, get_user_pages_fast() on a userspace address range containing foreign mappings does not work correctly because the M2P lookup of the MFN from a userspace PTE may return the wrong page. Force get_user_pages_fast() to fail on such addresses by marking the PTEs as special. If Xen has XENFEAT_gnttab_map_avail_bits (available since at least 4.0), we can do so efficiently in the grant map hypercall. Otherwise, it needs to be done afterwards. This is both inefficient and racy (the mapping is visible to the task before we fixup the PTEs), but will be fine for well-behaved applications that do not use the mapping until after the mmap() system call returns. Guests with XENFEAT_auto_translated_physmap (ARM and x86 HVM or PVH) do not need this since get_user_pages() has always worked correctly for them. Signed-off-by: David Vrabel <david.vrabel@citrix.com> Reviewed-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
65 lines
1.9 KiB
C
65 lines
1.9 KiB
C
/******************************************************************************
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* features.h
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*
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* Feature flags, reported by XENVER_get_features.
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*
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* Copyright (c) 2006, Keir Fraser <keir@xensource.com>
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*/
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#ifndef __XEN_PUBLIC_FEATURES_H__
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#define __XEN_PUBLIC_FEATURES_H__
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/*
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* If set, the guest does not need to write-protect its pagetables, and can
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* update them via direct writes.
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*/
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#define XENFEAT_writable_page_tables 0
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/*
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* If set, the guest does not need to write-protect its segment descriptor
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* tables, and can update them via direct writes.
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*/
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#define XENFEAT_writable_descriptor_tables 1
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/*
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* If set, translation between the guest's 'pseudo-physical' address space
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* and the host's machine address space are handled by the hypervisor. In this
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* mode the guest does not need to perform phys-to/from-machine translations
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* when performing page table operations.
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*/
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#define XENFEAT_auto_translated_physmap 2
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/* If set, the guest is running in supervisor mode (e.g., x86 ring 0). */
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#define XENFEAT_supervisor_mode_kernel 3
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/*
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* If set, the guest does not need to allocate x86 PAE page directories
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* below 4GB. This flag is usually implied by auto_translated_physmap.
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*/
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#define XENFEAT_pae_pgdir_above_4gb 4
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/* x86: Does this Xen host support the MMU_PT_UPDATE_PRESERVE_AD hypercall? */
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#define XENFEAT_mmu_pt_update_preserve_ad 5
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/*
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* If set, GNTTABOP_map_grant_ref honors flags to be placed into guest kernel
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* available pte bits.
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*/
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#define XENFEAT_gnttab_map_avail_bits 7
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/* x86: Does this Xen host support the HVM callback vector type? */
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#define XENFEAT_hvm_callback_vector 8
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/* x86: pvclock algorithm is safe to use on HVM */
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#define XENFEAT_hvm_safe_pvclock 9
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/* x86: pirq can be used by HVM guests */
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#define XENFEAT_hvm_pirqs 10
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/* operation as Dom0 is supported */
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#define XENFEAT_dom0 11
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#define XENFEAT_NR_SUBMAPS 1
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#endif /* __XEN_PUBLIC_FEATURES_H__ */
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